Well chubby is fine, but being fat actually brings too much health issues, but she actually exercises so my internet degree in health from the armchair uni really doesnt know what to think of this.
She should be fine medically. Female power lifter usually are fat but also have significant amount of muscle still. So basically body fat % is main thing that determines one's health.
That's literally the point of this chapter. They acknowledged that she gained a bit too much weight in the last chapter. So the two are exercising together to fix that.